1. Technical Field
The present invention relates to a wavelength separation device, a projector, and an image display system for performing three-dimensional image display.
2. Related Art
In the past, there has been known an image display system for stereoscopically expressing the display image. According to such an image display system, the observer views two images (a right-eye image and a left-eye image) shifted an amount from each other, the amount corresponding to the difference between the view points of the right eye and the left eye, namely so-called parallax images, selectively with the right and left eyes, respectively. Thus, the observer can visually recognize the display image stereoscopically.
As one system used in such an image display system, there has been known a wavelength separation system described in, for example, JP-A-2009-122659. The wavelength separation system is a system for projecting two parallax images having respective wavelengths different from each other, and then separating the right-eye image and the left-eye image thus projected by the difference in wavelength and sorting them into the left eye and the right eye respectively.
However, in the image display system (hereinafter referred to as an image display system 90) described in JP-A-2009-122659, there has been a problem explained below with reference to FIGS. 7, and 8A through 8D.
FIG. 7 is a block diagram showing a configuration of the image display system 90. Further, FIGS. 8A through 8D are diagrams for explaining the action of the image display system 90.
As shown in FIG. 7, the image display system 90 is configured including a projector PJ, a control section 91, a rotating wheel 92 (a filter), a screen SR, and a pair of observation spectacles 30.
The outgoing light L1 emitted from the projector PJ is transmitted through the rotating wheel 92, the outgoing light L2 is projected on the screen SR to thereby display an image in an enlarged manner.
In the projector PJ, image data (right-eye image data or left-eye image data) is input from an external device, and the projector PJ converts the image data into the outgoing light L1 of the right-eye image and the left-eye image shown in FIG. 8A, and then emits it alternately to the rotating wheel 92 in a time-divisional manner.
As shown in FIG. 8B, the rotating wheel 92 is configured including a disk section 92a, and a rotary support mechanism (not shown in FIG. 8B) for rotatably supporting the disk section. The disk section 92a is formed of an area A1 provided with a fan-shaped color filter and an area A2 provided with a fan-shaped color filter. These areas A1, A2 selectively transmit the colored lights (blue light LB, green light LG, and red light LR) in predetermined wavelength bands, respectively, out of the incident light. FIG. 8C is a diagram showing the transmittance characteristics of the areas A1, A2. In FIG. 8C, the transmittance characteristic in the upper part shows the transmittance of the area A1 with respect to the wavelength of the light, and the transmittance characteristic in the lower part shows the transmittance of the area A2 with respect to the wavelength of the light. As shown in FIG. 8C, the area A1 transmits the light with the wavelength on the lower side of the wavelength band of each of the blue light LB, the green light LG, and the red light LR, and blocks the light with the wavelength on the higher side of the wavelength band. Further, the area A2 transmits the light with the wavelength on the higher side of the wavelength band of each of the blue light LB, the green light LG, and the red light LR, and blocks the light with the wavelength on the lower side of the wavelength band.
The control section 91 controls the rotation of the disk section 92a via the rotary support mechanism in sync with the timing of sequentially emitting the outgoing light L1 of the right-eye image and the left-eye image to the rotating wheel 92. For example, the control section 91 controls the rotation of the disk section 92a so that the outgoing light L1 enters the area A1 of the disk section 92a during the period of emitting the outgoing light L1 of the right-eye image, and the outgoing light L1 enters the area A2 of the disk section 92a during the period of emitting the outgoing light L1 of the left-eye image. It should be noted that the control section 91 controls the rotation of the disk section 92a based on the information for distinguishing the right-eye image data and the left-eye image data from each other, included in the image data input to the projector PJ.
Thus, the rotating wheel 92 projects the outgoing light L2 of the right-eye image and the outgoing light L2 of the left-eye image different in wavelength from each other on the screen SR in a time-series manner.
The observer wears the pair of spectacles 30 in order to view the parallax image displayed on the screen SR as a stereoscopic image. The pair of observation spectacles 30 has a right side glass 30R and a left side glass 30L. In accordance with the area A1 of the rotating wheel 92, the right side glass 30R transmits the light with the wavelength on the lower side of the wavelength band of each of the blue light LB, the green light LG, and the red light LR, and blocks the light with the wavelength on the higher side of the wavelength band. Further, in accordance with the area A2 of the rotating wheel 92, the left side glass 30L transmits the light with the wavelength on the higher side of the wavelength band of each of the blue light LB, the green light LG, and the red light LR, and blocks the light with the wavelength on the lower side of the wavelength band. As described above, the transmittance characteristics of the right side glass 30R and the left side glass 30L of the pair of observation spectacles 30 are made to coincide with the transmittance characteristics of the areas A1, A2 of the rotating wheel 92, respectively. Therefore, the observer can view the right-eye image and the left-eye image respectively with the right eye and the left eye due to the difference in wavelength by wearing the pair of observation spectacles 30, and can therefore visually recognize the stereoscopic image in a “pseudo” manner due to the human visual feature.
Here, the rotating wheel 92 has a configuration in which the area where the outgoing light L1 enters from the projector PJ is switched between the areas A1 and A2 when the disk section 92a rotates. Therefore, the period when the outgoing light L1 enters both of the areas A1, A2 exists when the area where the outgoing light L1 enters is switched from either one of the areas A1 and A2 to the other. FIG. 8D is a diagram showing the period when the outgoing light L1 enters both of the areas A1, A2 translated with the central angles of the disk sections (the disk section 92a, and the disk section 92b). The upper part of the drawing shows the fact that the outgoing light L1 enters both of the areas A1, A2 in the period corresponding to the angle α in the disk section 92a. Further, the lower part of the drawing shows the fact that the outgoing light L1 enters both of the areas A1, A2 in the period corresponding to the angle β in the disk section 92b. As the measure for reducing the period in which the outgoing light L1 enters both of the areas A1, A2, the measure explained below can be considered. That is, assuming that the number of revolutions per unit time of the rotating wheel 92 is constant, the measure of elongating the radius of the disk section constituting the rotating wheel 92 to thereby reduce the period corresponding to the angle α to the period corresponding to the angle β as shown in the upper part and the lower part of the drawing shown in FIG. 8D can be considered. However, by elongating the radius of the disk section constituting the rotating wheel 92 as in the measure described above, there arises a problem of incurring the growth of the area of the rotating wheel, and causing the increase in size of the image display system 90.
Further, although the rotating wheel 92 (the filter) blocks the light with a predetermined wavelength out of the incident light (the outgoing light L1) as described above, the rotating wheel 92 actually reflects the light toward the projector PJ without absorbing the light. The light intensity of the reflected light corresponds to an amount a half as high as that of the incident light (the outgoing light L1). Therefore, in the projector PJ to which the reflected light is input, there is a possibility of heating the projector PJ to thereby cause the deterioration of the quality (the quality of the display image) of the outgoing light L1 in such a manner, for example, that the rise in temperature of the light source (lamp) constituting the projector PJ is incurred.